1. Field of the Invention
The present invention relates to an image processing system and a scanning electron microscope, and more particularly, to a function of performing process monitoring in, for example, semiconductor device manufacturing.
2. Background Art
Recently, thin film patterns formed on semiconductor wafers in the manufacturing process of semiconductor devices have been more and more miniaturized and highly integrated. There is an increasing need for automation of accurate and high-speed process monitoring for checking whether these thin film patterns are formed on wafers as designed.
As an inspection apparatus for measuring fine pattern dimensions, scanning electron microscopes (critical dimension-SEM (CD-SEM)) have been conventionally used as disclosed in, for example, JP Patent Publication (Kokai) No. 59-112217A (1984), JP Patent Publication (Kokai) No. 11-257939A (1999), JP Patent Publication (Kokai) No. 2000-28336A, and JP Patent Publication (Kokai) No. 2005-3416A. When pattern dimensions at a specified position on a semiconductor wafer placed on a CD-SEM stage (sample stage) are automatically measured, positioning by pattern matching using an SEM image of a measuring object is applied. Positioning on the SEM image is necessary because a measurement point is not matched due to the reasons in the measuring object side such that pattern formation on a wafer itself is misaligned, in addition to the reasons caused by a measuring apparatus such that accuracy of positioning by moving a stage is not adequate.
However, there often occurs a problem in the positioning by pattern matching. While basically a corresponding pattern portion is to be searched in the pattern matching, the dimensions of a measuring object to be measured are supposed to be changed, which conceptually contradict each other. It is therefore important that an element by which corresponding tendency is measured in the pattern matching is different from an element which is to be changed in the measuring object. When position accuracy by the pattern matching is not adequate, proper measurement values cannot be obtained. In the worst case, there is a possibility that measurement fails by misrecognizing a completely different pattern. Especially when the size of an object of the pattern matching is changed, the problem as described above occurs notably.
Therefore, as disclosed in JP Patent Publication (Kokai) No. 2006-31392A, a method of preparing a plurality of template images having different sizes to perform pattern matching has been proposed as the method of solving the case where the size of an object of the pattern matching is changed.